That's sort of true, but not always true Bob, for instance the IC-781 would
unload with a 300W spike when it felt like it and it was only a 150watt
radio. My amp would run at full power at 150Watts but put out super power
until parts flew out when the radio unleashed the BIG JUICE.
The answer without fixing the radio was have an amp that can take a 300 W
input spike.
The 781 has a fix for this problem, many of the other radio do not have one
yet.
BOB DD
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of rgroh@swbell.net
Sent: Monday, March 19, 2007 10:51 PM
To: Win; Amps@contesting.com
Subject: Re: [Amps] drive power
I think the problem being alluded to is a burst of RF (at full output) from
the transmitter/transceiver which happens before the ALC can cut in and
reduce it to the proper level. If the designer does pay attention, it is
easy to have happen - the RF turns on abruptly while the ALC loop has too
long of an attack time so there is a bit of time before the ALC loop can
come into play (delay time in the ALC loop). It certainly could, in some
units, be exaggerated when running at lower RF levels because you have
further for the ALC loop to ramp the output back.
The latter problem is also affected by the fact that the RF amplifier has a
maximum RF level (i.e. the RF is clipped or limited). If your normal RF
level is just a bit below the maximum then the 'burst' is not (relatively
speaking) not that much higher. For example, if your amplifier is only
capable of 150 W and you normally run 125W then the burst is only 25W
possible. If, on the other hand, you are running 25W normally then the
burst is 125W! Quite a difference.
Hope this helps a bit.
73
Bob, WA2CKY
Blue Springs, MO. 64014
----- Original Message ----
From: Win <w0lz@winlyn.us>
To: Amps@contesting.com
Sent: Monday, March 19, 2007 10:17:08 PM
Subject: Re: [Amps] drive power
I hate to come back to this subject, but I am not sure I understand the
problem. Is the overshoot a product of the ALC outputted from the exciter
to the amp, or is it caused within the transceiver at significantly reduced
power settings.
In either case I should be able to see the overshoot if I put a scope across
the meter in my power meter. Is that correct?.
I currently reduce my FT-1000MKV from 200 to 50 watts, when driving my old
SB-220 amp on CW.
Win, W0LZ
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